1. Field of the Invention
The present invention pertains to remote-control actuators. More particularly, the present invention pertains to the remote control of security systems.
2. Discussion of Related Art
Improvements in the design of remote-control devices for vehicle locking and alarm systems have increased the effective operating range of hand-held, keychain transmitters, which is now typically 75 feet to 150 feet. Operating range has frequently been mistakenly assumed to be desirable for its own sake. The progressive increase in the operating range is primarily due to the incorporation of features such as the remote car starting, remote trunk release, and remote window control, which provide improved security and convenience.
However, as the range of the convenience signals has increased, the range of the arming and disarming signals which are critical to the vehicle""s security has also been increased. This has, unintentionally, worked to the benefit of today""s sophisticated car thief, who now has a device known in the industry as a xe2x80x9ccode grabberxe2x80x9d.
This thief waits in a concealed area near the vehicle, within the operating range of the transmitter, until the vehicle""s operator returns and transmits the disarm signal. The code grabbing device receives and stores the operator""s disarm signal, which can now be retransmitted by the code-grabber device at a later time, disarming the vehicle""s alarm system and even unlocking and starting the vehicle for use by an unauthorized person, the thief.
In particular, most automotive alarm systems generate an audible tone or series of tones (xe2x80x9cchirpsxe2x80x9d) when armed or disarmed, which provide an audible indication to the user that the alarm system has indeed received the radio frequency (RF) signal from the transmitter and is responding. Many of these alarm systems also provide one or more flashes of the vehicle""s exterior lights as an added visual indication that the alarm system is responding to the hand-held transmitter.
Many of these alarm systems provide some means of eliminating the tone or series of tones that are sounded when arming and disarming the vehicle""s security system (xe2x80x9cchirp deletexe2x80x9d). These methods range from the installer activating a small dip switch located on the alarm controller module or cutting a wire loop on the alarm controller module to the operator""s repeated activation of a dashboard-mounted alarm control switch, pressing buttons on the keychain RF transmitter in a complex sequence which modifies the response of the remote control receiver.
There are several problems with these methods of chirp control. Systems that are installed with the audible chirp tones set either on or off cannot easily be changed by the alarm operator. Methods that do allow remote control by the operator are awkward to operate. They often leave the operator guessing, because they do not provide adequate confirmation. Push-button sequences are inconvenient because they are easy to forget and they are easily confused with the sequences that control other functions.
Additionally, these methods all set the alarm system controller into either a tone or no-tone mode of operation, and the system remains in that mode until the mode selection procedure is repeated. Thus the chirp delete option is generally not used.
The present invention greatly reduces the effective area in which a car thief can hide while operating a code grabbing device. It is much more difficult for the thief to conceal himself close to where the RF keychain transmitter is actuated, rather than 100 feet away.
This reduces the probability that a given vehicle can be stolen using a code grabber, thus reducing the overall number of such vehicles stolen and, hopefully, reducing the vehicle operators"" insurance premiums.
The present invention also provides a novel method of addressing the chirp delete feature. As the operator approaches the vehicle, system is armed and the operator presses the disarm button on the RF keychain transmitter for a short period of time, e.g., 0.5 seconds or less. The alarm system will then disarm and flash the vehicle""s parking lights as a visual confirmation, with a chirp for an audible confirmation. Alternatively, if the operator approaches the vehicle and holds the disarm button on the RF keychain transmitter pressed down for a slightly longer period of time, say between 0.5 seconds and 1.5 seconds, the alarm system disarms and provides visual confirmation, but there is no audible confirmationxe2x80x94the chirp is silent.
When the operator leaves the vehicle, the alarm system is disarmed and, if the arm button on the RF keychain transmitter is pressed for a short period of time, say 0.5 seconds, the alarm system will arm and provide a light flash and a chirp. Holding the arm button on the RF keychain transmitter down for the slightly longer period, 0.5 seconds to 1.5 seconds, causes the system to arm, but only flash the lights, not chirp.
The present invention provides a unique multi-range RF keychain transmitter circuit that reduces the effectiveness of code-grabber devices. The transmitted RF codes that control security features such as remote disarming and remote door unlock will have a limited operating range, which reduces the risk of automobile theft.
Another aspect of the invention provides a variable-range RF keychain transmitter that permits the transmission of codes that control convenience features such as remote car starting, remote trunk and window control, and remote headlight control, over a substantially greater operating range while preventing code-grabbing devices disarming the vehicle""s security system and unlocking the vehicle.
Another object of the invention is to provide an easily operated means of remotely selecting whether audible confirmation will or will not be provided during any given arm or disarm activation of the system.